As known in the art, the CD (compact disc) system currently employed as a main-current acoustic apparatus is of such a type that pits are formed in a 12 cm-diameter disc in a manner to correspond to digital PCM (pulse code modulation) data and reproduction is performed by, while rotating the disc in a drive rotation in a CLV (constant linear velocity) system, linearly tracking the data from an inner periphery side to an outer periphery side on the disc by a semiconductor laser and an optical pickup built in a photoelectric conversion element.
Audio playback musical tone data and sub-code data P, Q, R.about.W defined for control/display are recorded in the disc. Of the aforementioned data, the sub-code Q is also called as address data and represents, in a program area containing disc's musical tone data, a program number (TNO) of recorded musical tone data, a phrase number (INDEX), a lapse time (TIME) for each program, a total time (ATIME) lapsing from a start position of the program area, etc.
Further, the aforementioned sub-code data Q represents, in a lead-in area located on the inner periphery side of the program area, a start address of each program as TOC (table of contents) data. That is, the sub-code data Q is recorded for implementing a search operation, accurately at high speeds, for selective reproduction of playback data from vast information recorded in the disc to enable a stereo reproduction to be performed for about one hour and for grasping the sate of a reproduction on the disc.
The CD system has initially been developed so as to record and reproduce musical data. In recent years, with attention paid to such a vast recording capacity, a CD-ROM (read only memory) system is determined to be used as a read-only data recording medium for the disc through the use of a musical data recording area of the disc as a digital information recording area. The CD-ROM system is of such a type as to record and reproduce digital information on the disc without varying a recording/reproduction format for musical data reproduction in the CD system and to do so by adding a new format thereto.
In the conventional digital data processing system using the CD-ROM system, however, a disc reproduction section performs a reproduction on a disc where main digital data is recorded together with address data and outputs resultant main digital data to a host processing unit in a manner to be divided into a block unit corresponding to address data with the address data allocated to each block. If, therefore, the address data varies, by jitters, in a time-base direction, then no block/address data correspondence is obtained and a non-address-allocated block is not transferred to the host processing section, failing to perform a continuous data reproduction and presenting a problem.
The present invention is achieved with consideration paid to the aforementioned situation and the object of the present invention is to provide an excellent digital data processing apparatus which can perform a continuous data reproduction in an accurate block/address data correspondence relation.